Abstract
Laser micro-grooving has excellent potential to improve the surface properties of metals. In this study, high-speed micro-grooving of the surfaces of mild steel SS400 and aluminum alloy A1050 was investigated using a single-mode continuous-wave fiber laser with an average power of 200 W. Experiments were conducted at laser beam scanning speeds of 1 to 6 m/s. The incident angle of the laser beam in the plane perpendicular to the scanning axis was varied from 0 to 60°. A relatively deep groove (approximately 30 µm in depth) and a high upheaval (10 µm in height) were formed along the scanning line at an incident angle of 45° on the SS400, whereas only shallow grooves were formed on A1050. The micro-groove formation mechanism was discussed on the basis of high-speed camera observation, groove shapes, and the thermophysical properties of the metal. Asymmetric molten metal flow and solidification around the keyhole are thought to play important roles in micro-groove formation. Although the laser irradiation conditions must be optimized according to the thermophysical properties of the material, angled laser irradiation has the potential to effectively form micro-grooves.
Highlights
The laser source, processing method, and applications of laser surface micro-grooving have been widely investigated
In micro-grooving by angled laser irradiation, it is necessary to optimize the laser irradiation conditions according to the thermophysical properties of the material
CW fiber laser, and the formation mechanism of the micro-grooves was discussed using the results of high-speed camera observation
Summary
The laser source, processing method, and applications of laser surface micro-grooving have been widely investigated. If the shallow grooves could be appropriately controlled, effective micro-grooving by a CW laser might be possible, even at low average power Formation of these molten beads and shallow grooves are attributed to molten metal flow and solidification, which are symmetric with respect to the laser irradiation axis. When the balance of the molten metal behavior can be controlled by varying the incident angle of laser irradiation, it can be expected that deeper micro-grooves can be obtained by using a CW laser at lower power. Micro-grooving by angled laser irradiation of a low-average-power CW laser can be proposed as a new approach to deepening the shallow grooves that are formed at both edges of the molten bead.
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